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  1. #1
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    Help!

    Hi guys, please help me with these two questions:

    Find the speed in m/s of a point on a bicycle rim of diameter 88 cm, making 200 revolutions per minute.

    and

    Eight tins of paint are required for a surface of an area 50 m{square} if 4 coats of paint are applied. Find the number of tins of paint needed for an area of 70 m{square} if 5 coats of paint are applied.
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  2. #2
    MHF Contributor Quick's Avatar
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    Quote Originally Posted by laser2302
    Hi guys, please help me with these two questions:

    Find the speed in m/s of a point on a bicycle rim of diameter 88 cm, making 200 revolutions per minute.
    What you need to find first, is what is the circumference of the rim, which is 88\pi

    Now you need to find how many revolutions per second the rim goes, which is the amount rpm divide by 60 200\div60=3\frac{1}{3}

    now we multiply the circumference by the rps and we get the answer...

    88\pi\times3\frac{1}{3} that gives us cm/s so we divide by 100 to get m/s

    \frac{88\pi\times3\frac{1}{3}}{100} and that is the answer in m/s (I don't have a calc. handy so you need to solve)
    Quote Originally Posted by laser2302
    and

    Eight tins of paint are required for a surface of an area 50 m{square} if 4 coats of paint are applied. Find the number of tins of paint needed for an area of 70 m{square} if 5 coats of paint are applied.
    If 8tins are required for 4 coats, than only 2 tins are required for 1 coat. If 2 tins are required to cover 50m^2, than 1 tin will cover 25m^2.

    Now we need to figure out how many tins are required to cover 70m^2 with 1 coat. So we divide 70 by 25, 70m^2\div25m^2=2\frac{2}{5}

    so 2 and 2/5 tins are required for 1 coat, so now we multiply by 5 to get all 5 coats.

    2\frac{2}{5}\times5=12 therefore, 12 tins are needed.
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